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Manipal Medical Manipal Medical Solved Paper-2012

  • question_answer
    An electric motor runs on DC source of emf 200 V and draws a current of 10 A. If the efficiency be 40%, then the resistance of armature is

    A)  \[2\,\Omega \]             

    B)  \[8\,\Omega \]

    C)  \[12\,\Omega \]            

    D)  \[16\,\Omega \]

    Correct Answer: C

    Solution :

     Input power \[=VI=200\times 10\] \[=2000W\] Output power\[=\frac{40}{100}\times 2000=800W\] Power loss in heating the armature \[=2000-800\] \[=1200W\] \[\therefore \] \[{{I}^{2}}R=1200\] or      \[R=\frac{1200}{{{I}^{2}}}\] \[=\frac{1200}{10\times 10}\] or        \[R=12\,\Omega \]


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